Looks to be an iOS port of NewPipe, offering a $2.99 subcription to use.
Could be not horrible assuming it actually functions as newpipe does, but doesn't appear to be open source (found listed developers Github, no repository for this)
In terms of "are they allowed to", of course. They can take as much or as little of Newpipe as they'd like and monetize it however they like, as Newpipe is open source.
EDIT: The App Store does not facilitate releases under GPL licenses, so this is likely not acceptable behavior.
It would be covered under "common law" trademark rights even if the name and logo were not officially registered, as long as they can reliably prove the legitimate use of the name prior to the copycat.
It is not possible to release gpl software on the iOS App Store due to the extra licensing restrictions of apple.
That said, if you hold all the rights to the software, you can release your gpl software under a different license that is compatible with the App Store.
But it is currently violating the gpl if you take gpl software that you don’t have the ability to relicense and put it on the App Store.